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Six Patients Present with Complex Waveforms


As a relatively new nurse working in the emergency department, I remember a cardiologist who would come by before making his hospital rounds. He’d throw an ECG strip down on the desk, give us a quick scenario and ask, “What is it?” It was always an interpretation that would look obvious but involve more than met the eye. So when we’d give him a quick, but incorrect, answer, he’d respond with, “Gotcha!” He’d then explain the correct answer and be on his way. So I wanted to present a few cases to you and share some of the lessons I once learned. A snap judgment in medicine could prove disastrous for your patient.

These cases certainly don’t show the typical capnography waveforms. However, just like with ECG tracings, understanding the relationship between each component of the capnography waveform and each phase of the ventilatory cycle will help you understand what’s going on in these case studies.

Check out these interesting cases (see Gotcha! Gallery www.jems.com/photos/gotcha).

A Final Word
The case studies presented here are just a few of the many variations in capnography waveforms that may challenge your practice. Understanding the physiology of capnography and using this valuable assessment tool when indicated will help you to identify early warning signs of ventilatory or perfusion insufficiency, identify metabolic abnormalities, determine if medications are needed, improve cardiac arrest management, confirm appropriate ET tube placement, distinguish pulmonary from cardiac pathophysiology and generally provide better care to critical patients.

Pat Brandt, RN, has worked in EMS for more than 25 years as an EMS transport nurse, an emergency department nurse, a paramedic educator and an EMS quality manager. She recently retired as the EMS quality manager and paramedic instructor for Orange County (Fla.) Fire Rescue Department. She also served on the state committee in Florida that developed and supported the legislative rules requiring the use of continuous waveform capnography by Florida EMS agencies. Contact her at brandtp@bledsoe.net.

Disclosure: The author has completed contract work for Medtronic/Physio Control Corporation, a manufacturer that utilized Oridion capnography technology in their cardiac monitors.

This article originally appeared in the December 2010 JEMS supplement “Measuring Life & Breath” as “Gotcha!: Challenging waveforms that could fool an expert.”

1. Levine RL, Wayne MA, Miller CC. End-tidal carbon dioxide and outcome of out-of-hospital cardiac arrest. N Engl J Med. 1997;337:301–306.
2. Fearon, DM, Steele DW. End-tidal carbon dioxide predicts the presence and severity of acidosis in children with diabetes. Acad Emerg Med. 2002;9:1373–1378.
Additional Resources
•Krauss B. Advances in the use of capnography for non-intubated patients. Israeli. J Emerg Med. 2008;8:3–15.
•Lightdale JR, Goldmann DA, Fedlman HA, et al. Microstream capnography improves patient monitoring during moderate sedation: A randomized, controlled trial. Pediatrics. 2006;117:1170–1178.



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